Flexographic printing plates may be formed from a flexographic material having a photosensitive layer. In a computer-to-plate operation, an image to be printed exposes an ablatable masking material on a photopolymer plate to form a mask. The resulting mask is then uniformly exposed to ultraviolet (UV) radiation, and processed to form raised portions for use in printing. Thus, for certain flexographic materials, processing includes curing an exposed material with UV radiation in a UV exposure unit.
It is common to use cylindrical sleeves of flexographic plate material to form printing plates. After exposure to imaging data, the sleeves are transferred from the imager to a UV exposure unit and other processing machines. In order to match diameters the sleeve diameter to the size of specific machines, it is also common to place the sleeves on the outer surface of sturdy cylindrical sleeve adapters for imaging and and/or UV exposure.
For purposes of this description, the sleeve or sleeve adapter is a hollow cylinder. One technique for holding cylindrical sleeves and/or adapters is by using conical end pieces (chucks) and the apex of such conical chucks into each hollow end of the cylinder, and supporting the base of each conical end. The cylinder is held by friction. In a UV exposure unit, for example, one or both end pieces are then rotated while the sleeve is exposed to UV radiation from lamps. The lamps may either extend the length of the sleeve or are shorter than the length of the sleeve and move longitudinally as the sleeve is rotated.
There may be several problems with using such prior art UV exposure units with such conical chucks that are related to the alignment of the sleeve, access to the sleeve, and ability to expose different sized sleeves.
For accurate rotation, the axis of the cylinder should coincide with the two apexes of the chucks, i.e., with the axis of rotation. If each conical end piece easily slides into the respective end of the sleeve or sleeve adapter, then the sleeve will be aligned with the rotation axis. However, the pieces and sleeve or adapter do not always slide easily in practice, resulting in the axis of the cylindrical sleeve not being co-linear with the conical end pieces. As a result, the sleeve may not rotate properly about the sleeve axis.
Other problems with some prior art mechanisms relate to the fact that the diameters of different sleeves may vary.
Furthermore, access to the entire length of the sleeve may also be important, e.g., in order to UV expose all the way to the end of the sleeve. Since the ends are supported by conical end pieces having a base larger in diameter than the sleeve, for relatively small diameters it may not be possible to place a lamp near the sleeve ends. This can be overcome my having many conical chucks of different diameter to accommodate many different sleeve diameters. However, such an approach may not be desirable.
Reference symbols are used in the drawings to indicate certain components, aspects or features shown therein, with reference symbols common to more than one drawing indicating like components, aspects or features shown therein.